On Thursday, Raynaldo Rivera, 20, of Tempe, who used the online aliases of "neuron," "royal" and "wildicv" pleaded guilty in the U.S. District Court for the Central District of California to one count of conspiracy to intentionally cause damage without authorization to a protected computer.

In his plea agreement, the hacker admitted to joining LulzSec in May 2011 with the intention of helping the group carry out cyberattacks against businesses and government entities from the U.S. and around the world.

He also admitted to launching an SQL injection attack against sonypictures.com that allowed him to extract confidential and personal user information from the website's database. The information was later published online by LulzSec members.

"As a result of defendant's conduct, Sony Pictures suffered losses of approximately $605,663.67 during the one year period beginning on approximately May 27, 2011, including to hire computer forensic firms, to staff call centers, and to provide credit monitoring services for individuals whose personal identifying information was compromised," the plea agreement said.

Rivera surrendered to the FBI in Phoenix on Aug. 28 after being indicted on one count of conspiracy and one count of unauthorized impairment of data, programs, systems and information on a computer system used in interstate and foreign commerce and communication.

Rivera faced a statutory maximum sentence of 15 years in prison, but in exchange for his guilty plea, the U.S. Attorney's Office for the Central District of California agreed to drop the second charge and recommend a reduced sentence. Rivera's sentencing hearing is scheduled for March 14, 2013.

One of Rivera's co-conspirators in the Sony Pictures breach, a 23-year-old man from Phoenix named Cody Kretsinger who used the online moniker "Recursion", pleaded guilty in April to one count of conspiracy and one of unauthorized impairment of a protected computer.

Hector Xavier Monsegur, a 28-year-old hacker from New York who acted as the leader of LulzSec under the online alias of Sabu, was secretly arrested by the FBI in June 2011. He subsequently agreed to work as an FBI informant and it's believed that his collaboration with the authorities led to the arrest of other LulzSec members in the U.S. and other countries.